A novel series of 2-(m-Chlorobenzyl)-4-substituted-1, 1, 3-trioxo-2H, 4H-pyrazolo[4, 5-e][1, 2, 4] thiadiazines (7a-k) were synthesized, and evaluated for their anti-HIV replication in MT-4 cell cultures. Compound (7a) showed activity against HIV-1-induced cytopathicity, with an EC50 value of 45.6 microM, but none of the compounds exhibited inhibitory activity against HIV-2.